Map shows 122 kpa when the engine is off
 

Does anyone have an idea what might cause my Map to read 122 kpa when the engine is off. It reads this way both in Mega Tune and Tuner Studio. I just swapped injectors and had to replace the o-ring on the air valve. I wouldn't think it was the air valve because it does this when the engine is off. I also pulled off the source line going to the Map Daddy Sensor and the results were the same. The car of course is close to undrive able. Anyone have an idea what could have caused this.

I stepped down from 726cc injectors to 460's. I'm just wanting to drive the car with the 460's until I have enough cash for my swap.

(Posting from my phone.)

Its either the map sensor is bad, you live below sea level, or the calibration is wrong

Did the sensor ever read correctly? If so, what changed between then and now?

Does the reading from the sensor still move "normally"? Eg: if you were to stick a tube from the sensor into your mouth and blow or suck into it (there's no non-suggestive way to say that) does it do what you'd expect?

It does sound a tad like a miscalibration. Specifically, the voltage output from a normal MPX250 at 100kpa (atmospheric) would produce an indicated reading of 120kpa if the software were configured for an MPXH6300 (300kpa) sensor.

I guess it could be a miscalibration or a bad sensor. I was having issues with my larger injectors so I pulled them and but the 460's back in. When I pulled vacuum line going to the Map off and blew in it I didn't see a change on the display.

I change a few things, the tune as I went down from the 726's. I also replaced the o-ring on the air valve and put a new adjustment bolt on the alternator. I don't think either of those could cause this but I'm not going to say it can't happen.

After I started to car to see what it would do, it idle around 66-75 kpa. One other thing I noticed was the Fuel Map did not automatically rescale when I changed the Map sensor as I used the original 93 Non AFM Map as my base.

I went into the configurator in Megatune to change the MAP as well as select my wide band, but I will take a look again just to make sure. I changed the Map in Tuner Studio under projects.

Thank you both for looking at this.

I checked the previous settings and everything seemed fine. Just to be certain I reuploaded the firmware and reloaded an MSQ. I checked everything except the Dwell on my coils because I forgot the proper settings.

My Map is now reading 143-144, the current barometric pressure here is 30.15 in. Maybe it was in some other application but I thought you had to set the base Kpa in MegaTune, but I can't find that setting anywhere. I also looked at tuner studio, and again I cannot find a similar setting.

Looking at the mega manual it make a reference to an .inc file. Its said to be sure the proper .inc is loaded. Any idea which .inc it could be, or is that even the cause?

(Posting from my phone.)

Three actually. But that has to do with clt and ait tempps not map sensor

Do I have to specify map while the engine or give a base line anywhere during setup. I don't remember doing this in the past, but again I could be missing something. Is it maybe in the firmware update? The car will start but it behave very strangely.

Could the air valve effect this, or should I try refreshing the firmware once again with a different version.

The air valve is not going to create 6 PSI of boost.

Something is very wrong, and I'm honestly at a loss here.

Pop the lid off of the MS. With the engine off but the power on, take a voltmeter and measure between pin 23 of the CPU and ground. This is where the voltage from the MAP sensor enters the CPU.

Assuming that the MSPnP uses the standard 250kPa sensor (I think it does) you should see about 1.8 volts (the specified error for that sensor would put the acceptable range between appx 1.7 - 1.9 volts at 100 kpa.)

I'm using a 4 bar map, should I reset to a different sensor? Maybe set it two 250, and then test the voltage.

Ah.

Changing the software config won't change the sensor's output, it only changes how the CPU interprets that output.

But no worry, you can do the same test, just look for 1.2 volts (+/- 0.1v) at the pin, assuming 100kpa ambient.

Here's the scale of pressure to voltage for the 400 kpa sensor:

https://www.miataturbo.net/attachmen...ine=1319938482

You need to set your config for 4 bar map sensor. I'm guessing you set it for 1 bar.

i can confirm, on MS1 if you set it to the 250kpa sensor with a 4bar it reads about 120-130kpa.

If that's config as in configurator under megatune > file >configurator > MSPNP 9093 without AFM > settings.ini > settings> MAP_SENSOR i'm using MPXh6400A -- 400kpa

I went through everything again and now change. Then I removed all of the tuning software off my laptop redownlaoded everything and started from scratch just to make sure I wasn't uploading a corrupted file. So now I'm seeing slightly better but not great results. When I set the configurator to the 400 kpa sensor I'm seeing 110kpa in megatune. When I set the sensor to 300kpa, I see 82kpa. When I set the map under configurator to 250, I see 73kpa. Setting it to 115 shows nothing. Could I have a 350kpa sensor, and I don't have a setting for it?

crack open the case and try what joe suggested, also posting a pic of the sensor will allow everyone to identify it for you

dont use megatune. use tunerstudio.

I use MegaTune because the last few times I needed help from the guys at DIY they needed logs from MT. I also use MT to update firmware but thats only because I don't know of a way to do it in TunerStudio.

So this situation is anything but stable. With the engine not running and ignition off pin 23 to ground i get .988 or .989 at 106kpa. I also saw .991 at 104kpa. With the engine off, and the ignition on the meter shows 0.000.

https://www.miataturbo.net/attachmen...ine=1319997633

I was really confused so I went to pick up a new multi-meter. While going though the instructions I realized I was measuring resistance not voltage. It explains somethings but not others. So with the new meter set to measure voltage, I'm seeing 5.06-5.07 on pin 23 on the second board closest to the connector for the harness. And to answer Joe's earlier question, yes it sensor did seem to read correctly before, this is new behavior. Since it worked in the past should I just go through the boot jumper process and reload everything with the hope that maybe something was corrupted previously. BTW map kpa is listed as 106 now.

So under Basic Settings, Engine Constants, MAP sensor is set to 400kPa?

How close does the BARO sensor gauge read to your MAP sensor gauge?

Yes under engine constants is reads 400, and it has been since I upgraded from the 250 that came with the MS. It also list the 400 in the configurator. I also have extra sensor on x7 listed in the Baro settings. I have not checked the Baro gauge against the Map gauge, but I will do that when I get off work this afternoon.

To answer Joe's earlier question the voltage is 1.254

The engine map was listed as 109kpa, I will check the baro sensor when I get home tonight.

per the graph Joe provided this looks accurate for the voltage. But based on the pressure here in Plano it should be closer too 101.4. is this amount of fluctuation within spec. todays baron out side was 29.96, and my car is just sitting in the garage. I can't imagine the pressure would be that different.

The MAP Sensor Gauge and Baro Gauge both match.

I started the car this morning, and I'm seeing 109 kpa at idle. I saw 114 kpa before starting the car. Both the Map Gauge and Barometer Gauge seem in sync although the Barometer Gauge fluctuates a bit.

I'm lost as to what action to take next. It seems like maybe the Map sensor could have gone bad, but I'm not 100% positive of any of this.

not if both the sensors are outputting the same value. still sounds like a calibration error.

Do you have any idea where the bad settings or misconfiguration could be. I sent DIY screen shots of my configurator settings, but I have not heard back yet. If the configurator is correct, the voltage is within specs, the Constants are correct, and the Barometric settings are ok where could the issue be. I can't find any other places where the problem could be located.

Any suggestions on maybe just doing a clean install. I've done it already, but I will happily do it again if that might help.

Other than the settings.ini file can I specify the settings the MS uses then verify its using those specific settings without using megatune or tuner studio.

After trying everything suggested here and the suggestions from Matt and Ben I was ready to kick the car when I thought wow the map and baro are in sync when the engine isoff what happens when I start it. Again they stayed in sync at idle, so I reved the engine, and the Map didn't move but the engine vac gauge did. I thought what about that other nipple on the map sensor, so I swapped them and all of a sudden my map dropped from atmosphere (near atmosphere) to around 50kpa. That made me wonder about the tune so I started a new tune based on the original base map, and so foar its idle is much better. I haven't driven it yet since I have to put the MS back together, go to Denton, swing by the office and then do home work. Is it ok to use the other nipple, I thought I had been using he correct one all a long, but now I wonder if I made a mistake,

intersting.

Post a clear picture showing how you installed the mapdaddy to the MegaSquirt.

TO be sure I understand you correctly, when you refer to there being two nipples on "the map sensor", I assume that what you are calling "the map sensor" is the green daughterboard which is picture standing upright from the main board in post #18 of this thread?

If so, you should know that that board actually contains two separate MAP sensors. (Each of the two little black squares is one sensor.) One of them is the "main" MAP sensor, and the other is the sensor used for barometric pressure reading. So it sounds like you have had engine vacuum connected to the barometric pressure sensor this whole time?

You do understand correctly, however vacuum has been in the same place the whole time until I changed it today. I understand the Map Daddy has two sensors, and thats the kicker. I just changed it, today. I've had the map daddy in place since May or so. So unless someone is playing a pretty nasty joke somethings up.

I'll post photos tonight when I get back to the garage.

People on the adaptronic forum were having this kind of problem when the lower limit was set too high so it would read much higher than it really is. I dont know if MS has similar calibration settings.

I was sure when I first setup the MS I thought I had to put in the Map as read by the gauge for calibration, but I can't find any documentation on it any where, and no one else has mentioned doing it.

The baro limits should be set to 90-110kPa or so.

This is how the Map Daddy is currently connected.



https://www.miataturbo.net/attachmen...ine=1320684260

http://www.ntxbmx.com/lilred/4barmap2.jpg

http://www.ntxbmx.com/lilred/4barmap3.jpg

http://www.ntxbmx.com/lilred/4barmap4.jpg

That is the correct sensor for engine MAP.

I understand but that's not the one I was using. I was amazed how smoothly it fit into the case I was using the other sensor the whole time and for the most part it ran well. I was able to give my buell a break and drive to the miata to work. with the exception of working on the fine all seems well. I will try and leave it this way utill it goes in for the sawp at the endorse the year.

Sorry for the threadjack, but where might one source one of the threaded vacuum nipples as seen in this photo: http://www.ntxbmx.com/lilred/4barmap4.jpg I am assuming that it is a barb on each side with a short threaded body in the middle, right? My searches thusfar have not been very effective. :(

I know I can get it as part of the MapDaddy kit, but is it offered by itself somewhere?

Yes, we've got it in our Service Parts section.

http://www.diyautotune.com/catalog/b...ing-p-396.html

Thanks, Matt!